Diesel Generator Crankshaft Timing Gear Markings are Unclear

The assembly of the crankshaft timing gear and camshaft timing gear of diesel generators is a crucial step in repair, and the quality of their assembly directly affects the power and economy of the vehicle, which must be given sufficient attention.

During assembly, if both timing gears have timing marks, as the position relationship between the diesel generator gear and the crankshaft is determined by the keyway, it is only necessary to align the timing marks of the two gears and install them. If the timing marks of the two gears are unclear or unmarked, the following method can be used for assembly when knowing the valve timing angle of the intake and exhaust valves (this method is applicable to both large and small vehicle models and diesel vehicles, but the measurement location and installation method are different).

Before measurement, prepare a magnetic bracket and an indicator, adjust the connection relationship and valve clearance of the entire valve phase, and detach the crankshaft timing gear. During assembly, follow the following four steps.

1. Place the first cylinder piston at the top dead center position on the exhaust stroke. Pry the crankshaft flywheel to align it with the timing mark on the flywheel housing. At this time, observe the changes in the intake and exhaust valve rocker arms of the first cylinder by prying the flywheel clockwise and counterclockwise to determine whether the first cylinder piston is at the top dead center of the compression stroke or the top dead center of the exhaust stroke. When there is no change in the rocker arms of the intake and exhaust valves, it is at the top dead center of the compression stroke. When at the top dead center of the compression stroke, rotate the flywheel 360 ° to align the timing marks on the flywheel and flywheel housing. The position of the first cylinder piston is the top dead center of the exhaust stroke.

2. Determine the closing point of the first cylinder exhaust valve position. Rotate the camshaft timing gear. When you see the exhaust valve of the first cylinder turning from open to closed, stop rotating. Place the magnetic bracket near the exhaust valve, install the dial gauge, and place the contact pin of the dial gauge against the valve rocker arm. Then rotate the camshaft timing gear in the opposite direction to when it is closed. The moment the dial gauge starts to rotate, it stops rotating, which is the point where the exhaust valve is closed.

3. Determine the position of the corresponding piston when the exhaust valve is in the closed position. Because the transmission ratio between the crankshaft and camshaft is 2:1, the arc length corresponding to the delayed closing angle of the exhaust valve is 720/(2 π R θ） Mm (where R is the radius of the crankshaft, θ The angle is the late closing angle of the exhaust valve. At this time, rotate the flywheel clockwise so that it passes 720/(2 π R) from the exhaust timing mark point θ） The arc length of mm corresponds to the position of the piston when the exhaust valve is closed.

4. Rotate the camshaft to make contact between the intake valve rod and the tappet of the first cylinder, and install the crankshaft timing gear to ensure the correct assembly position of the two timing gears.

If the opening and closing angle of the intake and exhaust valves is not known, the following method can also be used to determine: rotate the crankshaft timing gear so that the piston of the first cylinder is at the top dead center (exhaust stroke top dead center or compression stroke top dead center) position, then remove the crankshaft timing gear, rotate the camshaft timing gear, so that the vertices of the intake and exhaust camshafts of the first cylinder are both upward or downward, and the contour lines of the two camshafts remain horizontal, And it should be in the shape of a "top eight" or "bottom eight", and installing the crankshaft timing gear at this position can ensure the correct assembly position.

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